For the major part of this century, dentists and veterinarians have treated and saved teeth by transcoronal root canal obturation. Most have used plain round and tapered pure silver or gutta percha composite obturator rods to occlude the round apical or tip area of the tooth which is embedded in bone and tissue. Generally this involves somewhat haphazardous or blind insertion of a glue or cement into the extirpated root canal, followed by an obturator rod. Smaller round rods then are inserted into the canal around the first rod and used to occlude the remaining space in the ovoid sections.
A variety of endodontic instruments have been disclosed for improving root canal extirpation and obturation. U.S. Pat. No. 5,017,138, for example, teaches a set of improved cutting instruments for reaming, filing and shaping root canals in preparation for obturation. U.S. Pat. Nos. 4,518,356, 2,453,696 and 1,067,015 likewise disclose various instruments and designs for extirpating root canals. Other art has focused on obturation as well, such as in U.S. Pat. No. 5,083,923 in which an obturation method is recited as comprised of a combination of thermoplasticized gutta percha introduced into the bottom of the root canal, followed by a gutta percha point which then is manipulated within the canal to compact the thermoplasticized gutta percha and thereby fill the root canal with a core of filler material. U.S. Pat. No. 4,740,245 discloses a filling composition comprising a polymer component, a copolymer resin and an insoluble or sparingly soluble inorganic filler.
A critical problem with root canal obturation not addressed adequately by the prior art related to endodontia is that insertion of a rod or any material into a closed end channel can cause the entrapment of air at the distal end. This air can cause "interior ballistic ignition" and "blow back" of material and glue. At the least it can cause misapplication of material at a critical point and result in failure of treatment.
Current endodontia instruments and practices do not provide for carrying cement or glue to the distal (apical) areas with sufficient accuracy, or combat hydraulic pressure and material displacement blow back. Additionally, the presently manufactured secondary cones or rods used for filling or occluding the ovoid sections of a tooth canal are usually quite small to allow for negotiation of the small canal spaces. This creates a number of problems; namely, low tensile strength of such small rods as observed in U.S. Pat. No. 4,740,245, at lines 4-10, leading to filling difficulty. Also, because smaller rods are used, as many as 5 to 10 such rods are needed thereby requiring significant practitioner time and effort to complete filling.
One object of the present invention therefore is to provide an improved device for obturating an extirpated root canal which enhances distal apical performance of sealer placement.
Another object of the present invention is to improve the integrity of sealer placed within the extirpated root canal by eliminating or minimizing air pockets and blow back of sealer.
Another object of the present invention is to improve the strength of the secondary obturator rods by design features to allow for fewer rods to be used and, in turn, result in a more solid obturation.
Another object of the present invention is to diminish the effects of hydraulic and ballistic problems in root canal fill procedures by obturator rod feature designs.
Still another object of the present invention is to reduce obturation treatment time by improved obturator design features.